Process of concentrating nitric acid.



TED STATES PAT F EK EIB'ERHARD BRAUER, OF LEIPZIG, GERMANY.

' PRO (JESS F CONCENTRATING NITRIC ACID.

No Drawing.

Specification of Letters Patent.

To all whom it may concern:

Be it known that I, EBERHARD BRAUER, a subject of the GermanEmp'eror, and resident of Leipzig, in the Kingdom of Saxony, German Empire, have invented new and useful Improvements in the Process of Concentrating Nitric Acid, of which the following is a full, clear, and exact specification.

Various methods 'or processes for concentrating nitric acid have been proposed" and used. The process hereinafter referred .to is an important improvement thereon. Sulfuric acid as a dehydrating agent in' concentrating dilute nitric acid by distillation possesses this disadvantage, that in adv di tion to the water with which it chemically combines to a considerable extent it also uniteswith the nitric acid itself, with the result that the boiling point of the mixture is remarkably increased whereby a considerable decomposition of the nitric acid takes place in addition to an increased expenditure of heat, as compared with the simple distillation. v

Salts such as caicium nitrate when used as. dehydrating agents have thedisadvantage that themixture when distilled be ins to foam, This causes technical difiiculties and the distillation products are thus subject to contamination. Further, whendistilling oif. the concentrated acid and the combined water the mass becomes solid. This causes local superheating, sudden shocks in the liquid and even explosions. Further the heating eifect is decreased in consequence of the bad transmission of heat from thewalls ofthevessellto the swelling'salt.

The ruse of g acids of the-phosphoric group, especially phosphoric and-arsenic acid, as comparedwith the above, possesses the following adyantages: They do not enter into; any chemical] combination with the nitric acid, but merely combine with the water. I which contains vbut littleyvater, from a mix-; ture of diluted nitricacidand phosphoric or arsenic acid, therefore does not require. any kind of decomposition of any chemical compopndg asis the case when employing sulfuric acid as a concentrating agent; There isjno danger of the mass becoming solid. f It is, therefore, neither? necessarytoemploy more heat than {required for n 1ere distillation,

cent.

The production of. a nitric ci which means a saving in fuel, nor is there anyfear of a decomposition of the nitric acid taking place. Hence, it is possible without any special manipulations to obtain as a product a nitric acid of a high percentage and free from nitric oxid.

In place of phosphoric acid or arsenic acid alone, a mixture of both acids may be used.

Examples.

concentrated by fractional distillation reason of its constant boiling point. During the distillation the first/fraction which passes with 97 per cent. strength in 30% of the pure nitric acid contained in the Patented Nov. 14. 1911. Application filed June 15, 1910. Serial No. 566,999.

original diluted nitric acid. The first ,86 per cent. of the quantity of pure nitric acid the original dilute nitricacid used, when collected together, will result in an acid of 94: per cent. strength. The next '14 per cent.

of the quantitywill still. contain 47 per Ultimately pure water will pass; When so conducting the process that the distillation is stopped only when nothing but pure water passes, the entire quantity of the form of nitric acid of 86.9 per cent. strength. A p

v.2. A; retort containing 100 kilograms of 1s. charged with 50'ldlograms of-nitric acid nitric acid employed will be recovered in syrupy phosphoric acid of 1.7 specific gravity I of 65, per cent; strength. On heating .nitric acid of nearly lOOper cent. strength is distilled ofi, the concentration decreasing when i'the distillation is continued. On. stopping the distillation when 80 per cent. of the absolute nitric acid contained in the diluted nitric acid used-have passed over, a nitric "acid of.92 per cent. strength is obtained.

3. A} retort is. charged with50 kilosof arsenic acid and 50 kilos ofphosphoric acid,

and 50'kilos of nitric acid of 65 per cent.

strength-are added. On heating the mixture the first fraction which distils off has a strength of somewhat more than 95 per cent.

and-is-AQ percent. of the pure nitric acid con'tainedj'n theloriginal diluted nitric acid. On stopping the distillation when 80 per cent. of the used quantity of pure nitric acid in the-original dilute nitric acid. have passed over, a nitric acid is obtained having an average strength of 92.6 per cent.

What I claim is 1. The process of concentrating nitric acid containing Water consisting in distilling said f dilnte acid in the presence of a. dehydratwhich consists in distilling nitric acid con- 10 taining Water with arsenic acid. 7

In testimony that I laim. the foregoing as my invention, I have signed my name in presence of two subscribing Witnesses.

EBERHARD BRAUER.

Witnesses I GERT. BONA,

H. J. DUNLAP. 

